Low Offset Spinning Current Hall Plate and Method to Operate it

ABSTRACT

One embodiment of the present invention relates to a method and apparatus for removing the effect of contact resistances for Hall effect device contacts. In one embodiment, the apparatus comprises a Hall effect device comprising a plurality of force and sense contact pairs. The force and sense contact pairs comprise a force contact and a separate and distinct sense contact. The force contact is configured to act as a supply terminal that receive an input signal while the sense contact is configured act as an output terminal to provide an output signal indicative of a measured magnetic field value. By utilizing separate contacts for inputting a signal (e.g., an applied current) and reading out a signal (e.g., an induced voltage) the non-linearities generated by contact resistances may be removed, thereby minimizing the zero point offset voltage of the measured magnetic field.

BACKGROUND OF THE INVENTION

Hall effect devices are often used in sensor applications forcontactless sensing of magnetic fields. Hall effect devices findwidespread use in many automotive and industrial applications. Forexample, in automotive applications a Hall effect device may be used tomeasure wheel speed in an automatic braking system (ABS) speed sensor,by measuring the speed of a magnet. In such an example, if a magnetapproaches a Hall sensor then the Hall sensor will measure an increasein the magnetic field, therefore allowing the speed of the wheel to bedetected.

Hall effect devices are solid state electron devices that operate inresponse to a magnetic field based upon the Hall effect principle, aphenomenon by which a voltage differential is generated across anelectrically conducting body in the presence of a magnetic field.Conventional Hall effect devices typically comprise a planar structure,known as a Hall plate, which is configured to generate an output signal(e.g., either voltage or current) that is proportional to an appliedmagnetic field.

Hall plates have orthogonal axes, such that applying a current along oneof the orthogonal axes causes a voltage to be generated along anotherorthogonal axis in the presence of a magnetic field. Typically, a Hallplate is operated by injecting a current into a first input, grounding aspatially opposed second input on the same axes, and measuring a voltagebetween inputs of an orthogonal set of axes. For example, as shown inFIG. 1, a current 104 may be applied across a two dimensional conductiveHall plate 102. According to the Hall principle, the presence of amagnetic field B causes the negative charge carrying particles of thecurrent 104 to vary their motion (according to the right hand rule asshown at 106) and generate an induced voltage differential between nodesV₁ and V₂, which is proportional to the magnetic field B.

The integration of Hall effect devices (e.g., Hall plates) intosemiconductor bodies (e.g., silicon substrate) has become common in manyapplications. One main problem of Hall effect devices is the zero pointoffset/error, which is a non-zero output signal (e.g., voltage, current)provided by the Hall effect device in the absence of a magnetic field(i.e., magnetic field equal to zero). The offset of Hall effect devicesis caused by small asymmetries of the device caused by manufacturingtolerances or mechanical stress or thermo-electric voltages. In order toreduce/remove the offset errors experienced by a Hall effect device, theHall effect device may be configured to take readings along differentorientations of the device. Such methods, known as “current spinning”,send current through a Hall effect device in different directions andcombine the output signals in a manner which reduces the offset. Forexample, a Hall effect device may be rotated by 90° between measurementsand then the average of the Hall output signals over a spinning cyclemay be taken. While current spinning methods may reduce the offseterrors (e.g. to 20 μT order of magnitude) such methods alone fail tocompletely remove the zero point error down to the noise level of 100 nT. . . 1 μT.

The cause of this residual zero point error is unclear. It can be proventhat it must vanish for Hall effect devices with perfectly linearvoltage-current-relationship. However, in modern CMOS technologiesjunction isolation techniques are used to isolate the Hall effectdevices from other circuit elements on the same substrate. The width ofthe depletion layers associated with these reverse biased junctionsdepends on applied potentials and this leads to nonlinearcurrent-voltage-characteristics of integrated Hall effect devices. Theabove stated small asymmetries of the Hall effect device are mixed up bythe nonlinearity of the device and result in higher order offset errorterms that cannot be eliminated by the spinning current principle.Therefore a method is sought to have a better control of the potentialsinside the Hall effect device during a spinning current cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a Hall plate, particularly showing the operatingprinciple of Hall effect devices.

FIG. 2 illustrates a top view of a first embodiment of a lateral Hallplate comprising a plurality of force and sense contact pairs.

FIG. 3 illustrates an equivalent circuit diagram of the lateral Hallplate shown in FIG. 2.

FIG. 4 illustrates a cross sectional view of the lateral Hall plateshown in FIG. 2.

FIG. 5 a illustrates a Hall plate having a plurality of dedicatedfeedback circuits coupled to respective force and sense contact pairs toregulate the potential at the sense contacts.

FIG. 5 b illustrates an exemplary feedback circuit comprising atransconductance input stage and Current Controlled Current Source.

FIG. 6 illustrates a Hall plate having a feedback circuit configuration,wherein feedback circuits are configured to provide currents at opposingsupply force contacts to keep the voltage potential at opposing outputsense contacts at a well defined value.

FIG. 7 a illustrates a Hall plate having a feedback circuitconfiguration comprising a differential feedback circuit.

FIG. 7 b illustrates an exemplary differential feedback circuit.

FIGS. 8 a-8 b illustrate additional alternative embodiments of Hallplate feedback circuit configurations, comprising feedback circuitsrespectively dedicated for a particular usage.

FIG. 9 illustrates an exemplary feedback circuit configuration whereinfeedback circuits are controlled using an adaptive control unit tochange one or more reference potential(s) during operation.

FIG. 10 illustrates a flow diagram showing an exemplary current spinningmethod.

FIGS. 11 a-d illustrates cross sectional cartoons of a vertical Halldevice illustrating the sequence of currents applied to the differentforce contacts of the Hall device.

FIG. 12 illustrates a flow diagram showing a method for reducing thezero point offset of a Hall plate.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described with reference to theattached drawing figures, wherein like reference numerals are used torefer to like elements throughout, and wherein the illustratedstructures and devices are not necessarily drawn to scale.

The inventor has appreciated that the zero point error observed inintegrated Hall effect devices may be related to the combination ofnonlinear current-voltage-characteristics and contact resistances. Forexample, when a current is input into a Hall plate terminal, the currentis subject to some non-zero contact resistance. The contact resistancecan produce a zero point offset/error signal that a spinning currentsequence does not remove.

Accordingly, a method and apparatus are provided herein for removing theeffect of contact resistances from Hall effect device measurements. Inone embodiment, the apparatus comprises a Hall effect device having aHall plate comprising a plurality of force and sense contact pairs,wherein respective force and sense contact pairs comprise a forcecontact configured to be supplied with an input signal and a sensecontact configured to provide an output signal indicative of a voltagepotential of the contact pair. By utilizing separate contacts forinputting a signal (e.g., an applied current) and reading out a signal(e.g., an induced voltage) the effect of contact resistances may besubstantially removed. For example, using a high impedance voltagemeasurement circuit (e.g., that applies a small current across the sensecontacts) to measure the voltage from a sense contact allows for thevoltage drop caused by the contact resistance to be minimized.

In one embodiment, the force and sense contact pairs may be coupled toone or more feedback circuits, configured to detect contact resistancesand to correct the voltage drop across these contact resistances. Inparticular, respective feedback circuits may be configured to receive asensed value from a sense contact. If the sensed value indicates avoltage drop between associated force and sense contacts, the feedbackcircuit can provide a feedback signal (e.g., current) at the forcecontact to adjust the voltage potential at the sense contact therebydefining any desired potential at the sense contact. The feedback signalgenerated by one or more feedback circuits may be measured and processedto generate a magnetic field value having a further reduced zero pointoffset.

FIG. 2 illustrates a top view of a first embodiment of a Hall effectdevice 200 comprising a plurality of force and sense contact pairs(contact pairs), as provided herein. In particular, each contact paircomprises a force contact/terminal 202 and a separate and distinct sensecontact/terminal 204. One or more force contacts 202 (e.g., F₁ and F₃)may be configured to receive an input signal (i.e., act as a supplyterminal), while one or more sense contacts 204 (e.g., S2 and S4) may beconfigured to provide an output signal (i.e., act as an outputterminal). Therefore, the use of force and sense contacts allows forseparate contacts to be used for providing an input signal and forreading an output signal. It also allows for a signal (e.g., current) tobe injected at a force contact (e.g., F₁) to control the voltagepotential at an associated sense contact (e.g., S₁).

For example, during typical operation of the Hall plate an appliedcurrent may be generated, through a conductive path in an active regionlocated between opposing contact pairs, by the injection of one or moresignals (e.g., currents) into spatially opposed force contact supplyterminals (e.g., injecting a first current into force contact F₁ and asecond current into force contact F₃), while a Hall voltage indicativeof an applied magnetic field can be measured across one or moreorthogonal sense contact output terminals (e.g., reading a voltage fromsense contact S₂ and sense contact S₄). Therefore, two force contactsupply terminals can be supplied with an input signal, while at leastone separate sense contact output terminal can provide an output signalindicative of a magnetic field acting on the Hall device.

Furthermore, in contrast to prior art Hall plates having two inputterminals to supply the plate with electrical energy and two outputterminals to provide an output voltage, the distinct force and sensecontacts of Hall effect device 200 may comprise as many output signalsas sense contacts. For example, as shown in FIG. 2, two sense contactsassociated with the supply terminals (e.g., S₁ and S₃) can be used tomeasure output signals that provide voltage potentials within the activeHall region (e.g., that do not depend on the applied magnetic field),while two additional sense contacts (e.g., S₂ and S₄), associated withthe output terminals provide an output signal (e.g., Hall voltage) thatdepends on an applied magnetic field. Therefore, the Hall effect devicemay provide output signals from both sense contact supply terminals andsense contact output terminals.

As shown in FIG. 2, the size of the force and sense contacts may vary indifferent embodiments. In one embodiment, the sense contacts S₁-S₄ maybe smaller than the force contacts F₁-F₄. For example, as shown in FIG.2, the size of sense contact S₃ is smaller in the lateral dimension thanthe size of force contact F₃ (e.g., s₁<s₂). Making the sense contactssmaller than the force contacts reduces short circuit effects of thesense contacts to the Hall voltage, but increases the internalresistance seen between the sense contacts (e.g., which increases thenoise of the Hall device). In one embodiment, the size of the sensecontacts may be chosen to reach a balance between the short circuiteffects and internal resistance.

The force and sense contact pairs may be symmetrically disposed over theHall plate. For example, in one embodiment shown in FIG. 2, the Hallplate comprises four contact pairs having a 90° symmetry. In such anembodiment, a second contact pair is spatially oriented at 90° withrespect to a first contact pair, a third contact pair is spatiallyoriented at 180° with respect to the first contact pair, and a fourthcontact pair is spatially oriented at 270° with respect to the firstpair. In other words, a line 206 between the centers of two opposingforce and sense contact pairs configured to operate as supply terminalcontact pairs is perpendicular to a line 208 between the centers of twoopposing force and sense contact pairs configured to operate as outputterminal contact pairs. In alternative embodiments, the Hall plate maycomprise three contact pairs having a 120° symmetry, or more than foursymmetric contact pairs (e.g., six contact pairs having a 60° symmetry,twelve contact pairs having a 30° symmetry, etc.).

FIG. 3 illustrates an equivalent circuit diagram 300 of the Hall plateof FIG. 2), showing contact resistances seen at the force and sensecontacts. In particular, the circuit diagram 300 illustrates theresistance of the Hall plate as six Hall plate resistors R1-R6 arrangedin a balanced bridge configuration. Resistors r1-r4 denote the contactresistances of the contacts.

The use of separate force contacts F₁-F₄ and sense contacts S₁-S₄ allowsfor voltage drops due to the contact resistances r1-r4 to be effectivelyavoided by making Hall voltage measurements through the sense contactsS₁-S₄ using a high impedance measurement device with low current.Therefore, as shown in FIG. 3, the sense contacts S₁- S₄ are shown asbeing “inside” of the force contacts F₁- F₄ since the sense contactsS₁-S₄ will not see the contact resistance r1-r4 during a Hall voltagemeasurement (i.e., the sense contacts S₁-S₄ will essentially avoid thecontact resistance associated with each contact of the Hall plate).

Accordingly, although both force and sense contacts have associatedcontact resistances, using the sense contacts for high-impedance voltagemeasurements allows the sense contact resistances to be ignored in themeasurement of an induced Hall voltage (illustrated in FIG. 3 by showingforce contact resistances but not sense contact resistances). Forexample, in one embodiment applied current(s) may be provided by acurrent source 302 to opposing force contacts, F₁ and F₃, to generate anapplied current within an active area of the Hall plate, which causes apotential difference between orthogonal opposing sense contacts S₂ andS₄ in the presence of a magnetic field. The use of separate force andsense contacts allows for the measurement of the potential difference tobe performed between the orthogonal opposing sense contacts S₂ and S₄using a high impedance voltage measurement circuit 304, therebyreducing/removing the voltage drop caused by the contact resistance(e.g., the voltage drop due to contact resistance seen by the highimpedance voltage measurement circuit is small according to Ohms lawV=IR, since the current is small due to the high impedance of thevoltmeter). In other words, the measurement of an induced Hall voltageat sense contacts is minimally effected by the contact resistances sincethe current of the measurement is small.

FIG. 4 illustrates a cross sectional view of a Hall plate 400 havingforce and sense contact pairs (e.g., corresponding to the Hall plate ofFIG. 2 and extending through contacts S₁, F₁ to S₃, F₃). It will beappreciated that the structure of the Hall plate illustrated in FIG. 4is a non-limiting embodiment intended to illustrate the inventiveconcept provided herein. One of ordinary skill in the art willappreciate that variations on the Hall plate cross section are conceivedas being included within the invention provided herein. For example, inan alternative embodiment a cross section of the Hall plate may comprisean n-type substrate having a small n-tub in a large p-tub, where thesmall n-tub is the Hall effect device and the junction isolation iseither between small n-tub and the large p-tub, the large p-tub andn-substrate, or both.

Referring to FIG. 4, the Hall plate 400 comprises a tub 404 having afirst doping type (e.g., lightly n-doped) that is formed within aconductive substrate 402 having a second doping type different than thefirst doping type (e.g., a p-doped region having 10¹⁵-10¹⁶ dopants/cubiccentimeter in CMOS). In various embodiments, the one or more tubs 404may comprise an implantation of the substrate, a diffusion, or epitaxiallayer. The opposite doping of the tubs 404 and the conductive substrate402 may cause junction isolation of the tubs 404 from a remainder of theconductive substrate 402 when appropriate bias conditions are applied.The junction isolation result in electrical nonlinearities in the Hallplate.

For example, the tub 404 and conductive substrate 402 may be biased soas to cause the junction between the tub 404 and conductive substrate402 to be reverse biased, resulting in a non-conducting depletionregion/layer 406 that causes an isolating p-n junction that isnon-conducting in one direction (e.g., a positive potential may beapplied to the tub while the substrate is grounded). The size of thenon-conducting depletion region/layer 406 may change based upon the sizeof the voltage applied across the isolation junction. For example, asthe reverse-voltage applied across the isolation junction increases thesize of the depletion layer 406 increases thereby causing electricalnon-linearities in the Hall effect device.

Force and sense contact pairs (e.g., F₁ and S₁, F₃ and S₃, etc.) arelocated within the tub 404. In one embodiment, the force and sensecontacts may be formed within highly doped contact implant regionshaving a higher doping than the tub 404. An active region 408 (where theHall effect takes place) is positioned laterally between the force andsense contact pairs. The thickness of the tub 404 is usually about 4 μmwith the force and sense contacts having a depth of between 1 μm to 2μm. The width of the tub 404 is usually between 50 μm to 100 μm, with aspacing between the force contacts and sense contacts (e.g., between F₁and S₁) being between 1 μm to 10 μm and a spacing between the sensecontacts S₁ and 5 ₃ being between 20 μm 100 μm.

Although FIG. 4 illustrates force contacts (e.g., F₁ and F₃) and sensecontacts (e.g., S₁ and S₃) formed within the same implantation tub, oneof ordinary skill in the art will be appreciated that the Hall effectdevice may comprise more than one tub, wherein the force and sensecontact may be formed within different tubs. For example, the forcecontacts (e.g., F₁ and F₃) may be formed within a deeper tub than thesense contacts (e.g., S₁ and S₃).

In one embodiment, a force contact (e.g., F₁) of a force and sensecontact pair may be disposed closer to perimeter of the Hall plate thanan associated sense contact of the contact pair (e.g., S₁) (i.e., thesense contacts are closer to the center of the hall plate and the forcecontacts are closer to its perimeter). As shown in FIG. 4, the distanced_(i) between the edge of force contact F₁ and the perimeter of the Hallplate is smaller than the distance d₂ between the edge of the sensecontact S₁ and the perimeter of the Hall plate. Such placement of aforce contact (e.g., F₁) allows for an applied current injected at theforce contact to travel through the Hall plate. In an additionalembodiment, the spacing between force and sense contacts d₃ (e.g.,spacing between F₃ and S₃) of a contact pair is smaller than the spacingbetween sense contacts d₄ (e.g., spacing between S₃ and S₁) of twoopposing contact pairs.

It will be appreciated that although FIGS. 2-4 illustrate a lateral Hallplate, that the lateral Hall plate configuration is a non-limitingembodiment of a Hall effect device that the present invention may beapplied to. One of ordinary skill in the art will appreciated that theforce and sense contact pairs provided herein may also be applied toother Hall effect devices (e.g., a vertical Hall effect device, forexample, wherein the vertical Hall effect device is arranged to sense amagnetic field extending generally parallel to the surface of thedevice, as shown below in, FIGS. 11 a-11 d).

In additional embodiments, the effect of the contact resistance on aHall effect device's zero point offset may be further reduced byspecifically controlling the voltage potential at the sense contactoutput terminals of the Hall effect device through the use of one ormore high impedance feedback circuits, configured to detect contactresistances and to correct the voltage drop across these contactresistances. In one embodiment, the one or more feedback circuits arecoupled to one or more force and sense contact pairs and are configuredto sense a voltage potential value at a sense contact and to providefeedback signals (e.g., currents) to an associated force contact,wherein the feedback signal defines the voltage potential at the sensecontact. Measurement of the feedback signals essentially allow for ameasurement of the induced Hall voltage without “seeing” voltage dropscaused by the resistance of the contacts.

For example, the resistance of a force contact causes current flowingacross the force contact to lead to a poorly defined voltage drop. Usingthe sense contacts, a high impedance feedback circuit can detect thispoorly defined voltage and provide a feedback signal that may add thesmall voltage drop back to generate a well defined potential. Forexample, to supply the Hall plate with 2V, a 2V potential may be appliedat force contact F₁. However, due to the resistance of the forcecontact, the high impedance feedback circuit may measure the potentialat an associated sense contact S₁ of +1.9V (because 0.1V got lost acrossthe contact resistance of the force contact). The feedback circuit canprovide a feedback signal at the force contact F₁ that accounts for thecontact resistance so that the sense contact S₁ will have the desired 2Vpotential.

Accordingly, in additional embodiments, the feedback signal generated byone or more output terminal feedback circuits may be measured over acurrent spinning cycle and processed to further remove zero point offsetvoltages caused by the residual effects of contact resistance remainingin a Hall effect device using force and sense contact pairs. FIGS. 5 a-8b illustrate various feedback circuit configurations that may be used tofurther remove a Hall effect device's zero point offset by activelycontrolling the voltage potential at various sense contacts of the Halleffect device (e.g., Hall plate). In particular, the FIGS. 5 a-8 billustrate different configurations that enable various operation modes(e.g., common-mode operation, differential operation, etc.) for a Halleffect device.

It will be appreciated that FIGS. 5 a-8 b illustrate a single clockphase of a current spinning cycle. Over a complete current spinningcycle the illustrated reference potentials and/or feedback circuitconnections may be cycled to change the applied and induced current overa over a 360° rotation. For example, FIG. 5 a illustrates the referencepotential values (e.g., U₁=2V, U₃=0.5V) at a first clock cycle 1, whileat a second clock cycle 2 the reference potentials may be rotated by 90°(e.g., so that U₂=2V and U₄=0.5V), and at third clock cycle 3 thereference potentials may be rotated by 180° (e.g., so that U₃=2V andU₁=0.5V), and at a fourth clock cycle 4 the reference potentials may berotated by 270° (e.g., so that U₄=2V and U₂=0.5V). Furthermore, it willbe appreciated the sequence of clock cycles (e.g., clock cycles 1, 2, 3,4) may be reversed to clock cycles 4-3-2-1 or may be changed to clockcycles 1-3-2-4, clock cycles 1-3-4-2, or even a stochastic reassignmentto eliminate thermo-electric errors. One may also use several Halleffect devices with different sequences of clock cycles for bettersuppression of zero point offset voltages.

In one embodiment, shown in FIG. 5 a, a Hall effect device 500 maycomprise a plurality of feedback circuits 504 coupled to respectiveforce and sense contact pairs of a Hall plate 502 to regulate thevoltage potential at the sense contacts at well defined values (e.g.,the potential at sense contact S₁ is controlled by dedicatedfeedback-circuit FB_(I), the potential at sense contact S₂ is controlledby dedicated feedback-circuit FB₂, etc.). In particular, by coupling thefeedback circuits 504 to a force contact and a sense contact pair (e.g.,coupling a high impedance feedback circuit input node to one or moresense contacts and a feedback circuit output node to one or more forcecontacts), a feedback loop is formed that provides a feedback signal(e.g., feedback current I_(n), where n=1,2,3,4) to a force contact inorder to keep the voltage potential at an associated sense contact at awell defined voltage potential value. For example, feedback circuit FB₁may be configured to provide a feedback current I to a force contact F₁in order to keep the electrical potential at an associated sense contactS₁ at a well defined voltage potential. Such a feedback circuitconfiguration allows for control of the differential voltage and/or thecommon-mode voltage between the orthogonal spatially opposed sensecontacts output terminals.

Since each contact pair comprises distinct force and sense contacts,each sense contact may provide an output signal to an associatedfeedback circuit. For example, as shown in FIG. 5 a, sense contacts S₁and S₂, associated with the supply terminals, can be used to measureoutput signals that provide output potentials within the active Hallregion (e.g., that do not depend on the applied magnetic field) toassociated feedback circuits FB₁ and FB₃. Sense contacts S₂ and S₄,associated with the output terminals, provide an output a signal thatdepends on the applied magnetic field.

In one embodiment, two of the feedback circuits may be configured toachieve well defined voltage potentials at spatially opposed supplyterminals, while two additional feedback circuits may be configured toachieve well defined voltage potentials that are substantially the samefor orthogonal spatially opposed output terminals. For example, ifreference potentials U₁ and U₃ are set to different values (e.g.,reference potential U₁=3V, reference potential U₃=0.5V) feedbackcircuits FB₁ and FB₃ will respectively provide currents I₁ and I₃ toforce contacts F₁ and F₃, to drive associated sense contacts to adifferent voltages that causes an applied current to flow in the activeregion of the Hall effect device (e.g., from S₁ to S₃). In the absenceof a magnetic field, the voltage potential at the sense contacts S₄ andS₂ are at the same potential. However, the presence of a magnetic fieldthe applied current generates an induced voltage that causes the voltagepotentials at sense contacts S₂ and S₄ to be different. If the voltagepotentials at S₂ and S₄ are controlled to be identical in the presenceof a magnetic field, the feedback circuits FB₂ and FB₄ will respectivelyprovide feedback currents I₂ and I₄ to achieve the identical voltagepotentials.

In one embodiment, a processing unit 506 may measure the differencebetween the feedback currents applied to the orthogonal spatiallyopposed output sense contacts (e.g., I₂ and I₄), over a spinning cycle,to effectively remove the effect of the residual zero point offset dueto contact resistances. In particular, the difference between thefeedback currents, I₂ and I₄, provided to spatially opposed sensecontacts is essentially linearly dependent (i.e., wherein linearlydependent means (I₄−I₂)=k*B+c, where B is the magnetic field, k is aconstant, and c is the offset) so that the difference between feedbackcurrents, I₂ and I₄, can be measured and processed (e.g., subtracted)over a full spinning cycle to provide for a magnetic field measurementhaving a reduced zero point offset.

FIG. 5 b illustrates an exemplary feedback circuit 508 (e.g.,corresponding to feedback circuit FB₁ in FIG. 5A) comprising atransconductance input stage TC₁ and Current Controlled Current SourceCCCS₁. The transconductance input stage TC₁ comprises a positivenon-inverting input (+) and a negative inverting input (−). Thetransconductance input stage TC₁ is configured to output a currentI_(TC) that is proportional to the voltage between its non-inverting (+)and inverting (−) inputs. If the voltage at the non-inverting input ispositive against the inverting input, the output current is positive. Ifthe voltage at the non-inverting input is negative against the invertinginput, the output current I_(TC) is negative.

The output current I_(TC) of the transconductance stage TC₁ is providedto CCCS₁, which outputs a feedback current I₁ to a force contact F₁ todrive the voltage potential at an associated sense contact to thereference voltage potential U₁ (e.g., feedback current I₁ is provided toF₁ to drives the voltage potentials at S₁ to be equal to U₁). If TC₁comprises a large factor of proportionality, a small voltage differencebetween the inverting inputs can provide a large output current toCCCS₁, since I₁ is proportional to current and is independent of thecontact resistance to which the current is supplied.

Therefore, during operation if the voltage potential at a sense contact(e.g., S₁) is lower than the reference or target voltage potential ofthe feedback circuit (e.g., U₁), the feedback circuit (e.g., FB₁)injects a large positive current (e.g., I₁) into the a force contact(e.g., F₁) of the Hall effect device to raise the potential at the sensecontact (e.g., S₁) until it is equal to the reference voltage (e.g.,U₁). Similarly, if the voltage potential at a sense contact (e.g., S₁)is higher than the reference or target voltage potential of the feedbackcircuit (e.g., U₁), the feedback circuit (e.g., FB₁) drastically reducesits output current supplied to a force contact (e.g., F₁) of the Halleffect device, thereby lowering the potential at the sense contact(e.g., S₁) until it is equal to the reference voltage (e.g., U₁).

In one embodiment, the reference voltage potential may be chosen toguarantee that a feedback circuit sources a current to the forcecontacts. For example, if feedback circuits FB₁ and FB₃ are configuredto respectively have reference potentials U₁=2V and U₃=0.5V, at zeromagnetic field a non-linear Hall plate may have a voltage potential of1.1V at S₂ and S₄. A standard deviation of an offset voltage at zeromagnetic field of 1.3 mV (e.g., a six-sigma value of 7.8 mV) and amaximum voltage swing measurable between S₂ and S₄ of 20 mV, due tomaximum applied magnetic field, provide for a potential at S₂ and S₄having an upper limit of 1.1V+(7.8 mV+20 mV/2)=1.1178 V. Therefore,choosing U₂=U₄=1.2 V causes CCCS₂ and CCCS₄ to source current.

FIG. 6 illustrates an alternative embodiment of a Hall plate feedbackcircuit configuration 600, wherein two feedback circuits, FB₁ and FB₃,are coupled to spatially opposed force and sense contact pairs. Feedbackcircuits FB₁ and FB₃ are configured to source current to opposing forcecontact supply terminals to set the voltage potentials at S₁ greaterthan the voltage potential at S₃ (e.g., U₁=3V, U₃=0.5V), thereby causingthe feedback circuits to generate an applied current that flows in theactive region of the Hall plate. In particular, a feedback circuit FB₁generates a feedback current I₁ that is provided to the force contact F₁to keep the voltage potential at an associated sense contact S₁ at afirst well defined value. Similarly, a feedback circuit FB₃ generates afeedback current I₃ that is provided to the force contact F₃ to keep thevoltage potential at an associated sense contact S₃ at a second welldefined value, smaller than the first well defined value. Since thereare no feedback circuits coupled to S₂ and S₄, the Hall plate is leftfree to establish some voltage potential at S₂ and S₄. A measurementelement 604 is configured to measure the voltage potential between S₂and S₄. Measured voltages may be processed by a processing unit 606configured to compute a magnetic field value from the measured voltage,over a full spinning cycle to compute a magnetic field with a reducedzero point offset.

Therefore, FIG. 6 uses feedback circuits to drive a current at the forcecontact supply terminals of the Hall device, in contrast to FIG. 5 a,which uses feedback circuits in both force contact supply terminals andsense contact output terminals of the Hall device.

FIG. 7 a illustrates another alternative embodiment of a Hall platefeedback circuit configuration 700 comprising feedback circuitsconfigured to operate in a differential operating mode. As shown in FIG.7 a, feedback circuits FB₁ and FB₃ are coupled to spatially opposedforce and sense contact pairs to generate an applied current in theactive region of the Hall plate. A differential feedback circuitFB_(DIFF) is configured to measure an induced voltage differentialbetween sense contacts S₂ and S₄. Based upon the measured voltagedifferential, the differential feedback circuit FB_(DIFF) is configuredto generate a differential feedback current I₄ that is provided to forcecontact F₄, to control the voltage difference between sense contacts S₂and S₄ so as to form a well defined voltage potential differencetherebetween. Therefore, as shown in FIG. 7 a the differential feedbackcircuit FB_(DIFF) is configured to provide a differential feedbackcurrent I₄ that is proportional to the difference in voltage potentialbetween sense contact S₂ and sense contact S₄ so that the voltagedifference across S₂-S₄ is equal to 0 V. By measuring the differentialfeedback current output from the differential feedback circuit FB_(DIFF)over a full spinning cycle, and processing the measured differentialfeedback currents, a magnetic field having a reduced zero point offsetcan be computed.

FIG. 7 b illustrates an exemplary differential feedback circuit 704corresponding to difference node 702 a and feedback circuit 702 b inFIG. 7 a. As shown in FIG. 7 b, the differential feedback circuit 704may have a transconductance input stage TC_(DIFF) that acts as a simpleoperational amplifier, such that the input signals received at thedifferential inputs, IN_(S2) and IN_(S4), comprise the voltage potentialat sense contacts S₂ and S₄. The transconductance input stage TC_(DIFF)outputs a current I_(TC), proportional to the voltage between itsdifferential inputs, to a Current Controlled Current Source CCCS_(DIFF)that outputs a differential feedback current I₄ to a force contact F₄ todrive the differential voltage between sense contacts S₄ and S₂ to areference value (e.g., U_(DIFF))

FIGS. 8 a and 8 b illustrate additional alternative embodiments of Halleffect device feedback circuit configurations, comprising feedbackcircuits respectively dedicated for a particular usage. In particular,FIGS. 8 a and 8 b illustrate a dedicated source-feedback circuitFB_(SRC), a dedicated sink-feedback circuit FB_(SNK), a dedicatedcommon-mode feedback circuit FB_(CM), and a dedicated differentialfeedback circuit FB_(DIFF). The dedicated source feedback circuitFB_(SRC) may be configured to generate a high-voltage feedback signalthat drives a supply terminal contact pair of the Hall effect device toa high voltage. The dedicated sink-feedback circuit FB_(SNK) may beconfigured to generate a low-voltage feedback signal that drives anopposite supply terminal contact pair of a low voltage. The dedicatedcommon-mode-feedback circuit FB_(CM) may be configured to generate afeedback signal that drives orthogonal output terminal contact pairs tomid-level voltage potential (e.g., (S₂+S₄)/2), while the dedicateddifferential feedback circuit FB_(DIFF) may be configured to generate afeedback signal that drives orthogonal output terminal contact pairs tozero differential output voltage.

In such an embodiment, the Hall effect device feedback circuitconfiguration may further comprise a switch matrix 802 configured toconnect the dedicated feedback circuits to contact pairs according to asequence of clock cycles, so that each feedback circuit operates for itsdedicated purpose. The use of dedicated feedback circuits may allow foroptimization of the feedback circuits for their dedicated use. Forexample, the differential feedback circuit FB_(DIFF), which determinesthe difference of currents used to force the voltage potential acrossorthogonal sense contacts to zero, may be optimized for low noise,whereas the other three feedback circuits are allowed to be lesssensitive to noise.

Furthermore, during operation the use of dedicated feedback circuits mayallow for the system to be operated in two ways: using the differentialfeedback circuit FB_(DIFF) to control a difference in voltage (e.g., setdifferential feedback voltage=0 V) between orthogonal sense contactoutput terminals (e.g., S₂ and S₄), or to use the common-mode feedbackcircuit FB_(DIFF) to control the absolute voltage (e.g., set common modevoltage potential=1.2 V) of the orthogonal sense contact outputterminals.

For example, as shown in FIG. 8 a, Hall effect device feedback circuitconfiguration 800 comprises a common-mode feedback circuit FB_(CM)configured to receive the sum of voltage potentials at sense contacts S₂and S₄. In one embodiment, the summation may be performed within thecommon-mode feedback circuit FB_(CM). The common-mode feedback circuitFB_(CM) divides the summation of voltage potentials by two and outputs acurrent I₂ that drives sense contacts S₂ and S₄ to a voltage potentialequal to (S₂+S₄)/2 (L e., sets U_(CM)=(S₂+S₄)/2). Since I₂ may bepositive or negative, the common mode feedback circuit is capable ofgenerating a bipolar output current (i.e., is capable of sourcing andsinking output currents).

The differential feedback circuit FB_(DIFF) is configured to receive thedifference of voltages potentials at sense contacts S₂ and S₄ and tocompare the difference to 0V. In one embodiment, the difference may becalculated within the differential feedback circuit FB_(DIFF) (e.g., asshown in FIG. 7 b). The differential feedback circuit FB_(DIFF) thenoutputs a current I₄ that drives sense contacts S₂ and S₄ to adifferential voltage potential of zero volts. Since I₄ may be positiveor negative, the differential feedback circuit is capable of generatinga bipolar output current (i.e., is capable of sourcing and sinkingoutput currents).

FIG. 8 b illustrates an alternative embodiment of a Hall effect devicefeedback circuit configuration 804 wherein each of the differentialfeedback circuit FB_(DIFF) and common mode feedback circuit FB_(CM)comprise two feedback outputs F_(A) and F_(B). The common-mode feedbackcircuit FB_(CM) has two feedback outputs F_(A) and F_(B), configured tooutput identical feedback currents. The differential feedback circuitFB_(DIFF) also has two feedback outputs F_(A) and F_(B), configured tooutput inverted outputs (e.g., F_(A)=F_(B)). Therefore, if thedifferential feedback circuit FB_(DIFF) sources a current at F_(A) itsinks the same current at F_(B), and vice versa.

In one embodiment, the feedback circuits may be controlled using anadaptive control unit 902 to change the reference potential duringoperation, as shown in FIG. 9. In particular, the adaptive control unit902 may be coupled to a Hall effect device feedback circuitconfiguration 904 (e.g., corresponding to the Hall effect devicefeedback circuit configurations shown in FIGS. 5 a, 6, 7 a, 8 a, 8 b)and is configured to control the reference potentials U_(x) (x=1, . . .4) using some adaptive control techniques. For example, in oneembodiment the adaptive control unit 902 can observe the averagefeedback currents that are injected into output contact pairs (e.g.,into contact pairs 2 and 4 in the 1st and 3rd clock phases and intocontact pairs 1 and 3 in the 2nd and 4th clock phases). The adaptivecontrol unit 902 can then compute the time average over several fullclock sequences (e.g. over 2 or 200 or 20000 cycles) and can adjust thereference potentials until the average feedback current into the outputpairs is zero.

FIG. 10 illustrates a flow diagram of an exemplary current spinningmethod for a Hall plate having a plurality of force and sense contactpairs, as provided herein, over a spinning cycle comprising a pluralityof clock phases (e.g., clock phases 1002, 1008, 1014, and 1018). Whilemethod 1000 is illustrated and described below as a series of acts orevents, it will be appreciated that the illustrated ordering of suchacts or events are not to be interpreted in a limiting sense. Forexample, some acts may occur in different orders and/or concurrentlywith other acts or events apart from those illustrated and/or describedherein. In addition, not all illustrated acts may be required toimplement one or more aspects or embodiments of the disclosure herein.Also, one or more of the acts depicted herein may be carried out in oneor more separate acts and/or phases.

Furthermore, the claimed subject matter may be implemented as a method,apparatus, or article of manufacture using standard programming and/orengineering techniques to produce software, firmware, hardware, or anycombination thereof to control a computer to implement the disclosedsubject matter (e.g., the circuit shown in FIG. 5 a is non-limitingexamples of circuits that may be used to implement method 1000). Theterm “article of manufacture” as used herein is intended to encompass acomputer program accessible from any computer-readable device, carrier,or media. Of course, those skilled in the art will recognize manymodifications may be made to this configuration without departing fromthe scope or spirit of the claimed subject matter.

FIGS. 11 a-11 d illustrate exemplary cross sectional cartoons of avertical Hall device 1100. Input and output terminals comprise contactsF₁, S₁, . . . S₄. F₄, which are located at the surface of the die (e.g.,with wires on top of them), while rectangle 1102 denotes the is lightlyn-doped tub. The vertical Hall device 1100 has a geometry comprising along narrow strip with the input and output terminals lined up at asingle straight line and in alternating sequence, so that there is aninput terminal between two output terminals (e.g., F₂ between S₂ and S₃)and vice versa (e.g., S₂ between F₁ and F₂). FIGS. 11 a-11 d shows asequence of currents applied to the different force contacts of thevertical Hall device during the plurality of clock phases of method1000, illustrating that the use of force-sense-contact pairs in avertical Hall device.

At 1004, during the first clock phase 1002, a voltage potential at sensecontact S₁ is set to a value greater than a voltage potential at sensecontact S₃, thereby resulting in a current flowing from force contact F₁to force contact F_(3,) as shown in FIG. 11 a. Furthermore, currents I₂and I₄ are provided to force contacts F₂ and F₄, to set the voltagepotential at sense contact S₂ equal to the voltage potential at sensecontact S₄.

At 1006, during the first clock phase 1002, the difference between theapplied currents, I₄−I₂, is calculated.

At 1010, during the second clock phase 1008, a voltage potential atsense contact S₂ is set to a value greater than a voltage potential atsense contact S₄, thereby resulting in a current flowing from forcecontact F₂ to force contact F₄, as shown in FIG. 11 b. Furthermore,currents I₃ and I₁ are provided to force contacts F₃ and F₁, to set thevoltage potential at sense contact S₃ equal to the voltage potential atsense contact S₁.

At 1012, during the second clock phase 1008, the difference between theapplied currents, I₁−I₃, is calculated.

At 1016, during the third clock phase 1014, a voltage potential at sensecontact S₃ is set to a value greater than a voltage potential at sensecontact S₁, thereby resulting in a current flowing from force contact F₃to force contact F₁, as shown in FIG. 11 c. Furthermore, currents I₄ andI₂ are provided to force contacts F₄ and F₂, to set the voltagepotential at sense contact S₄ equal to the voltage potential at sensecontact S₂.

At 1014, during the third clock phase 1014, the difference between theapplied currents, I₂−I₄, is calculated.

At 1022, during the fourth clock phase 1020, a voltage potential atsense contact S₄ is set to a value greater than a voltage potential atsense contact S₂, thereby resulting in a current flowing from forcecontact F₄ to force contact F₂, as shown in FIG. 11 d. Furthermore,currents I₁ and I₃ are provided to force contacts F₁ and F₃, to set thevoltage potential at sense contact S₁ equal to the voltage potential atsense contact S₃.

At 1024, during the fourth clock phase 1020, the difference between theapplied currents, I₃−I₁, is linearly dependent to the contactresistance.

At 1026 the computed differences between the applied currents are summed(e.g., (I₄−I₂)+(I₁−I₃)+(I₂−I₄)+(I₃−I₁)). The summed difference islinearly dependent to the applied magnetic field and substantiallyvanishes (i.e., has an offset error below 1 μT) at zero magnetic field.In one embodiment, the supply voltages applied in clock phases 1002,1008, 1014, 1020 are equal, which means the potential at S₁ of clockphase 1002=potential at S₂ of clock phase 1008=potential at S₃ of clockphase 1014=potential at S₄ of clock phase 1020; and the potential at S₃of clock phase 1002=potential at S₄ of clock phase 1008=potential at S₁of clock phase 1014=potential at S₂ of clock phase 1020. Therefore, asshown in FIGS. 10-11 a-11 d, a Hall effect device having one or morefeedback circuits may reduce/remove a zero point offset by determiningfeedback currents in different orientations of the Hall effect device,the circuit can compute a signal that is linearly dependent to theapplied magnetic field and that substantially vanishes at zero magneticfield.

FIG. 12 illustrates a flow diagram of an exemplary method 1200 forreducing a zero point offset error of a Hall effect device.

At 1202 an input signal is applied to opposing force contact supplyterminals, respectively comprised within spatially opposed force andsense contact pairs of a Hall effect device, to assign well definedvoltage potentials to associated sense contacts of the Hall effectdevice. The well defined voltage potentials may be chosen so as togenerate an induced current in an active region located between thespatially opposed force and sense contact pairs. In one embodiment thewell defined voltage potentials may be assigned to be different atopposing force and sense contact pairs, causing an induced current toflow in an active region of the Hall effect device. In one embodiment,feedback circuits are configured to apply feedback signals to opposingforce contact supply terminals to generate well defined voltagepotentials at opposing force and sense contact pairs, causing an inducedcurrent to flow in an active region of the Hall effect device.

At 1204, the voltage potential of one or more orthogonal sense contactoutput terminals is optionally held at a well defined voltage potential.In one embodiment, one or more currents are output from one or morefeedback circuits to orthogonal opposing sense contact output terminalsto drive the voltage potential of the opposing sense contacts to asingle well defined value.

At 1206 one or more output signals associated with one or moreorthogonal sense contact output terminals of the Hall effect device aremeasured. The output signals associated the one or more orthogonal sensecontact output terminals is proportional to an applied magnetic field.In one embodiment, the output signals may be measured directly from thesense contact output terminals of the orthogonal contact pairs (e.g., asshown in FIG. 3). In an alternative embodiment, the outputs signals maybe measured from feedback current(s) output from one or more feedbackcircuits to the orthogonal contact pairs (e.g., as shown in FIGS. 5 a).

Line 1208 indicates that the method of steps 1202-1206 may be repeatedmultiple times, before proceeded to step 1210, when the method is usedin a current spinning cycle. For example, in a Hall plate having contactpairs comprising a 90° symmetry, steps 1202-1206 will be repeated fourtimes before proceeding to step 1210, while in a Hall plate havingcontact pairs comprising a 60° symmetry, steps 1202-1206 may be repeatedsix times before proceeding to step 1210.

At 1210 the measured signals are processed to compute a magnetic fieldvalue. In one embodiment the measured signals may comprise feedbackcurrents measured over a spinning current cycle. In one embodiment, acomputed difference between the feedback currents applied to opposingsense contact output terminals can be summed over a complete spinningcycle to achieve a magnetic field value.

The invention provided herein is typically illustrated and describedwith respect to lateral Hall plate configurations (e.g., in FIGS. 2, 5 a6, etc.). However, it will be appreciated that this is one non-limitingembodiment of a hall effect device to which the present invention may beapplied. One of ordinary skill in the art will appreciate that theinvention disclosed herein may be applied to various physicalembodiments of Hall elements, which rely upon the Hall effect to detecta magnetic field. For example, although FIGS. 2-4 illustrates force andsense contact configurations with respect to a lateral hall plate, theinventive concept of the force and sense contacts may be applied to anyHall effect device (e.g., a vertical hall plate).

Although the invention has been illustrated and described with respectto one or more implementations, alterations and/or modifications may bemade to the illustrated examples without departing from the spirit andscope of the appended claims. In particular regard to the variousfunctions performed by the above described components or structures(assemblies, devices, circuits, systems, etc.), the terms (including areference to a “means”) used to describe such components are intended tocorrespond, unless otherwise indicated, to any component or structurewhich performs the specified function of the described component (e.g.,that is functionally equivalent), even though not structurallyequivalent to the disclosed structure which performs the function in theherein illustrated exemplary implementations of the invention. Inaddition, while a particular feature of the invention may have beendisclosed with respect to only one of several implementations, suchfeature may be combined with one or more other features of the otherimplementations as may be desired and advantageous for any given orparticular application. Furthermore, to the extent that the terms“including”, “includes”, “having”, “has”, “with”, or variants thereofare used in either the detailed description and the claims, such termsare intended to be inclusive in a manner similar to the term“comprising”.

1. A Hall effect device, comprising: a conductive substrate having afirst doping type; one or more tubs having a second doping typedifferent than the first doping type, wherein an application of biasconditions to the Hall effect device allows for formation of anon-conducting depletion region, which causes junction isolation,between the tubs and the conductive substrate; and a plurality of forceand sense contact pairs respectively comprising distinct force contactsand sense contacts located within the one or more tubs, whereinrespective force contacts are configured to provide electrical energy tothe Hall effect device and respective sense contacts are configured toprovide an output signal from the Hall effect device.
 2. The Hall effectdevice of claim 1, wherein the Hall effect device comprises a 90°symmetry between force and sense contact pairs such that a line betweenthe centers of two opposing force and sense contact pairs configured tooperate as supply terminals is perpendicular to a line between thecenters of one or more force and sense contact pairs configured tooperate as output terminals that provide the output signal proportionalto an applied magnetic field.
 3. The Hall effect device of claim 1,wherein the sense contacts of both contact pair supply terminals andcontact pair output terminals are configured to provide output signalsproportional to a voltage potential at a respective sense contact. 4.The Hall effect device of claim 1, wherein the force contact ofrespective force and sense contact pairs is disposed closer to theperimeter of the Hall effect device than the sense contact of the forceand sense contact pair.
 5. The Hall effect device of claim 1, where aspacing between force and sense contacts of respective force and sensecontact pairs is smaller than a spacing between sense contacts ofopposing force and sense contact pairs.
 6. The Hall effect device ofclaim 1, wherein the Hall effect device comprises a vertical Hall effectdevice, comprising the input force contacts and output sense contactsaligned in a single straight line and in alternating sequence.
 7. TheHall effect device of claim 1, further comprising a plurality offeedback circuits coupled to the plurality of force and sense contactpairs and configured to control a voltage potential at a sense contactof a force and sense contact pair of the Hall effect device by providingone or more feedback signals to the force contact of the sense contactpair, wherein processing measured feedback signals provided to a forcecontact of one or more output terminal contact pairs over a currentspinning cycle provides a magnetic field value with a substantially zeropoint offset voltage.
 8. The Hall effect device of claim 7, furthercomprising an adaptive control unit configured to control a referencepotential value associated with respective feedback circuits of the Halleffect device using an adaptive control technique, wherein respectivefeedback circuits of the Hall effect device drive the voltage potentialat respective force and sense contact pair to the reference potential.9. A Hall effect device, comprising: a plurality of force and sensecontact pairs disposed on a Hall effect device, wherein respective forceand sense contact pairs comprise a force contact configured to receivean input signal and a separate sense contact configured to provide anoutput signal, wherein the plurality force and sense contact pairs areconfigured to provide at least two supply terminals, located along afirst axis and configured to receive the input signal and at least oneoutput terminal, located along a second axis perpendicular to the firstaxis and configured to provide the output signal indicative of amagnetic field acting on the Hall effect device.
 10. The Hall effectdevice of claim 9, further comprising: one or more feedback circuitscoupled to one or more of the plurality of force and sense contactpairs, respective feedback circuits configured to generate a feedbacksignal that controls a voltage potential at a coupled sense contact,wherein the one or more feedback circuits comprise a high impedancefeedback circuit input node coupled to one or more sense contacts and afeedback circuit output node coupled to one or more force contacts. 11.The Hall effect device of claim 10, wherein respective feedbackcircuits, comprise: a transconductance input stage having a first inputnode configured to receive an input signal from the one or more sensecontacts, a second input node configured to receive a reference signal,and an output node configured to output a current proportional to thevoltage difference between the first and second input nodes; and acurrent controlled current source configured to receive the outputsignal and to generate a feedback current based thereupon that isprovided to the one or more force contacts associated with the one ormore sense contacts.
 12. The Hall effect device of claim 10, wherein theone or more feedback circuits comprise: first and third feedbackcircuits respectively coupled to spatially opposed first and thirdcontact pairs, the first and third feedback circuits configured togenerate first and third feedback currents that establish a first andthird potentials at opposed first and third sense contacts.
 13. The Halleffect device of claim 12, wherein the one or more feedback circuitsfurther comprise: second and fourth feedback circuits respectivelycoupled to spatially opposed second and fourth contact pairs, the secondand fourth feedback circuits configured to generate second and fourthfeedback currents that establish an equal voltage potential at secondand fourth sense contacts, wherein the difference between the second andfourth feedback currents is essentially linearly dependent of themagnetic field acting on the Hall effect device.
 14. The Hall effectdevice of claim 12, further comprising a differential feedback circuitcoupled to spatially opposed second and fourth contact pairs, thedifferential feedback circuit having an input configured to receive avoltage potential difference between second and fourth sense contactsand an output configured to provide a differential feedback current thatreduces the potential difference between the second and fourth sensecontacts.
 15. The Hall effect device of claim 12, further comprising: acommon-mode feedback circuit coupled to spatially opposed second andfourth contact pairs, the common-mode feedback circuit having an inputconfigured to receive a summation of the voltage potential at second andfourth sense contacts and further having an output configured to providea common-mode feedback current that drives the potential differencebetween the second and fourth sense contacts to be equal to the sum ofthe voltage potential at the second and fourth sense contacts divided bytwo.
 16. The device of claim 10, wherein the one or more feedbackcircuits comprise: a dedicated source-feedback circuit configured togenerate a first voltage potential at a first sense contact of the Halleffect device; a dedicated sink-feedback circuit configured to generatea second voltage potential at a third sense contact spatially opposed tothe first sense contact, wherein the second voltage potential is smallerthan the first voltage potential; a differential feedback circuitconfigured to generate a voltage potential of substantially zero onopposing second and forth sense contacts orthogonal to the first andthird sense contacts; a common-mode feedback circuit configured togenerate a common-mode voltage potential on the second and forth sensecontacts, which is smaller than the first voltage potential and largerthan the second voltage potential; and a switch matrix configured toconnect the one or more of feedback circuits to the force and sensecontact pairs according to a sequence of clock cycles.
 17. The halleffect device of claim 10, further comprising: an adaptive control unitconfigured to control reference potentials associated with the one ormore feedback circuits using an adaptive control technique, whereinrespective feedback circuits of the Hall effect device drive the voltagepotential at a coupled force and sense contact pair to the associatedreference potential.
 18. The device of claim 9, wherein contact pairscomprising the force and separate sense contacts allow for measurementof an induced Hall voltage to be performed between two output terminalscomprising opposing sense contacts using a high impedance voltagemeasurement circuit, thereby reducing the effect of contact resistanceon the measurement.
 19. A method for reducing zero point offset in aHall effect device, comprising: applying input signals to force contactsupply terminals, comprised within spatially opposed force and sensecontact pairs, to generate an induced current in an active regionlocated between the spatially opposed force and sense contact pairs;measuring an output signal proportional to an applied magnetic fieldassociated with one or more orthogonal sense contact output terminalsover a current spinning cycle; and processing the measured output signalover the current spinning cycle to compute a magnetic field value. 20.The method of claim 19, further comprising: providing a feedback signalthat holds the potential at one or more orthogonal sense contactterminals at a substantially equal voltage potential; wherein measuringthe output signal comprises measuring the feedback signal over thecurrent spinning cycle.